TRIM3, a tumor suppressor linked to regulation of p21(Waf1/Cip1.)

EF1α-associated protein complexes affect dendritic spine plasticity by regulating microglial phagocytosis in Fmr1 knock-out mice

Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability. There is no specific treatment for FXS due to the lack of therapeutic targets. We report here that Elongation Factor 1α (EF1α) forms a complex with two other proteins: Tripartite motif-containing protein 3 (TRIM3) and Murine double minute (Mdm2). Both EF1α-Mdm2 and EF1α-TRIM3 protein complexes are increased in the brain of Fmr1 knockout mice as a result of FMRP deficiency, which releases the normal translational suppression of EF1α mRNA and increases EF1α protein levels. Increased EF1α-Mdm2 complex decreases PSD-95 ubiquitination (Ub-PSD-95) and Ub-PSD-95-C1q interaction. The elevated level of TRIM3-EF1α complex is associated with decreased TRIM3-Complement Component 3 (C3) complex that inhibits the activation of C3. Both protein complexes thereby contribute to a reduction in microglia-mediated phagocytosis and dendritic spine pruning. Finally, we created a peptide that disrupts both protein complexes and restores dendritic spine plasticity and behavioural deficits in Fmr1 knockout mice. The EF1α-Mdm2 and EF1α-TRIM3 complexes could thus be new therapeutic targets for FXS.

TRIM3 facilitates ferroptosis in non-small cell lung cancer through promoting SLC7A11/xCT K11-linked ubiquitination and degradation

Ferroptosis, a unique form of regulated necrotic cell death, is caused by excessive iron-dependent lipid peroxidation. However, the underlying mechanisms driving ferroptosis in human cancers remain elusive. In this study, we identified TRIM3, an E3 ubiquitin-protein ligase, as a key regulator of ferroptosis. TRIM3 is downregulated in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), two major types of non-small cell lung cancer (NSCLC). Forced expression of TRIM3 promotes cell death by enhancing the cellular level of ROS and lipid peroxidation. Moreover, our in vivo study determined that TRIM3 overexpression diminishes the tumorigenicity of NSCLC cells, indicating that TRIM3 functions as a tumor suppressor in NSCLC. Mechanistically, TRIM3 directly interacts with SLC7A11/xCT through its NHL domain, leading to SCL7A11 K11-linked ubiquitination at K37, which promotes SLC7A11 proteasome-mediated degradation. Importantly, TRIM3 expression exhibits a negative correlation with SCL7A11 expression in clinical NSCLC samples, and low TRIM3 expression is associated with a worse prognosis. This study reveals that TRIM3 functions as a tumor suppressor that can impede the tumorigenesis of NSCLC by degrading SLC7A11, suggesting a novel therapeutic strategy against NSCLC.

Ribogenesis boosts controlled by HEATR1-MYC interplay promote transition into brain tumour growth

Cell commitment to tumourigenesis and the onset of uncontrolled growth are critical determinants in cancer development but the early events directing tumour initiating cell (TIC) fate remain unclear. We reveal a single-cell transcriptome profile of brain TICs transitioning into tumour growth using the brain tumour (brat) neural stem cell-based Drosophila model. Prominent changes in metabolic and proteostasis-associated processes including ribogenesis are identified. Increased ribogenesis is a known cell adaptation in established tumours. Here we propose that brain TICs boost ribogenesis prior to tumour growth. In brat-deficient TICs, we show that this dramatic change is mediated by upregulated HEAT-Repeat Containing 1 (HEATR1) to promote ribosomal RNA generation, TIC enlargement and onset of overgrowth. High HEATR1 expression correlates with poor glioma patient survival and patient-derived glioblastoma stem cells rely on HEATR1 for enhanced ribogenesis and tumourigenic potential. Finally, we show that HEATR1 binds the master growth regulator MYC, promotes its nucleolar localisation and appears required for MYC-driven ribogenesis, suggesting a mechanism co-opted in ribogenesis reprogramming during early brain TIC development.

It's a TRIM-endous view from the top: the varied roles of TRIpartite Motif proteins in brain development and disease

The tripartite motif (TRIM) protein family members have been implicated in a multitude of physiologies and pathologies in different tissues. With diverse functions in cellular processes including regulation of signaling pathways, protein degradation, and transcriptional control, the impact of TRIM dysregulation can be multifaceted and complex. Here, we focus on the cellular and molecular roles of TRIMs identified in the brain in the context of a selection of pathologies including cancer and neurodegeneration. By examining each disease in parallel with described roles in brain development, we aim to highlight fundamental common mechanisms employed by TRIM proteins and identify opportunities for therapeutic intervention.

TRIM67 drives tumorigenesis in oligodendrogliomas through Rho GTPase-dependent membrane blebbing

BACKGROUND

IDH mutant gliomas are grouped into astrocytomas or oligodendrogliomas depending on the codeletion of chromosome arms 1p and 19q. Although the genomic alterations of IDH mutant gliomas have been well described, transcriptional changes unique to either tumor type have not been fully understood. Here, we identify Tripartite Motif Containing 67 (TRIM67), an E3 ubiquitin ligase with essential roles during neuronal development, as an oncogene distinctly upregulated in oligodendrogliomas.

METHODS

We used several cell lines, including patient-derived oligodendroglioma tumorspheres, to knock down or overexpress TRIM67. We coupled high-throughput assays, including RNA sequencing, total lysate-mass spectrometry (MS), and coimmunoprecipitation (co-IP)-MS with functional assays including immunofluorescence (IF) staining, co-IP, and western blotting (WB) to assess the in vitro phenotype associated with TRIM67. Patient-derived oligodendroglioma tumorspheres were orthotopically implanted in mice to determine the effect of TRIM67 on tumor growth and survival.

RESULTS

TRIM67 overexpression alters the abundance of cytoskeletal proteins and induces membrane bleb formation. TRIM67-associated blebbing was reverted with the nonmuscle class II myosin inhibitor blebbistatin and selective ROCK inhibitor fasudil. NOGO-A/Rho GTPase/ROCK2 signaling is altered upon TRIM67 ectopic expression, pointing to the underlying mechanism for TRIM67-induced blebbing. Phenotypically, TRIM67 expression resulted in higher cell motility and reduced cell adherence. In orthotopic implantation models of patient-derived oligodendrogliomas, TRIM67 accelerated tumor growth, reduced overall survival, and led to increased vimentin expression at the tumor margin.

CONCLUSIONS

Taken together, our results demonstrate that upregulated TRIM67 induces blebbing-based rounded cell morphology through Rho GTPase/ROCK-mediated signaling thereby contributing to glioma pathogenesis.

Dual roles of TRIM3 in colorectal cancer by retaining p53 in the cytoplasm to decrease its nuclear expression

Colorectal cancer is a very heterogeneous disease caused by the interaction of genetic and environmental factors. P53, as a frequent mutation gene, plays a critical role in the adenoma-carcinoma transition during the tumorous pathological process. Our team discovered TRIM3 as a tumor-associated gene in CRC by high-content screening techniques. TRIM3 demonstrated both tumor-suppressive and tumorigenic features in cell experiments dependent on the cell status of wild or mutant p53. TRIM3 could directly interact with the C terminus of p53 (residues 320 to 393), a common segment of wtp53 and mutp53. Moreover, TRIM3 could exert different neoplastic features by retaining p53 in the cytoplasm to decrease its nuclear expression in a wtp53 or mutp53-dependent pathway. Chemotherapy resistance develops in nearly all patients with advanced CRC and seriously limits the therapeutic efficacies of anticancer drugs. TRIM3 could reverse the chemotherapy resistance of oxaliplatin in mutp53 CRC cells by degradation of mutp53 in the nuclei to downregulate the multidrug resistance gene. Therefore, TRIM3 could be a potential therapeutic strategy to improve the survival of CRC patients with mutp53.

TRIM56 promotes malignant progression of glioblastoma by stabilizing cIAP1 protein

BACKGROUND

The tripartite motif (TRIM) family of proteins plays a key role in the developmental growth and therapeutic resistance of many tumors. However, the regulatory mechanisms and biological functions of TRIM proteins in human glioblastoma (GBM) are not yet fully understood. In this study, we focused on TRIM56, which emerged as the most differentially expressed TRIM family member with increased expression in GBM.

METHODS

Western blot, real-time quantitative PCR (qRT-PCR), immunofluorescence (IF) and immunohistochemistry (IHC) were used to study the expression levels of TRIM56 and cIAP1 in GBM cell lines. Co-immunoprecipitation (co-IP) was used to explore the specific binding between target proteins and TRIM56. A xenograft animal model was used to verify the tumor promoting effect of TRIM56 on glioma in vivo.

RESULTS

We observed elevated expression of TRIM56 in malignant gliomas and revealed that TRIM56 promoted glioma progression in vitro and in a GBM xenograft model in nude mice. Analysis of the Human Ubiquitin Array and co-IPs showed that cIAP1 is a protein downstream of TRIM56. TRIM56 deubiquitinated cIAP1, mainly through the zinc finger domain (amino acids 21-205) of TRIM56, thereby reducing the degradation of cIAP1 and thus increasing its expression. TRIM56 also showed prognostic significance in overall survival of glioma patients.

CONCLUSIONS

TRIM56-regulated post-translational modifications may contribute to glioma development through stabilization of cIAP1. Furthermore, TRIM56 may serve as a novel prognostic indicator and therapeutic molecular target for GBM.

TRIM family contribute to tumorigenesis, cancer development, and drug resistance

The tripartite-motif (TRIM) family represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. TRIM family is involved in a variety of cellular signaling transductions and biological processes. TRIM family also contributes to cancer initiation, progress, and therapy resistance, exhibiting oncogenic and tumor-suppressive functions in different human cancer types. Moreover, TRIM family members have great potential to serve as biomarkers for cancer diagnosis and prognosis. In this review, we focus on the specific mechanisms of the participation of TRIM family members in tumorigenesis, and cancer development including interacting with dysregulated signaling pathways such as JAK/STAT, PI3K/AKT, TGF-β, NF-κB, Wnt/β-catenin, and p53 hub. In addition, many studies have demonstrated that the TRIM family are related to tumor resistance; modulate the epithelial–mesenchymal transition (EMT) process, and guarantee the acquisition of cancer stem cells (CSCs) phenotype. In the end, we havediscussed the potential of TRIM family members for cancer therapeutic targets.

TRIM7 modulates NCOA4-mediated ferritinophagy and ferroptosis in glioblastoma cells

Objective

Glioblastoma is one of the most common intracranial malignant tumors with an unfavorable prognosis, and iron metabolism as well as ferroptosis are implicated in the pathogenesis of glioblastoma. The present study aims to decipher the role and mechanisms of tripartite motif-containing protein 7 (TRIM7) in ferroptosis and glioblastoma progression.

Methods

Stable TRIM7-deficient or overexpressing human glioblastoma cells were generated with lentiviral vectors, and cell survival, lipid peroxidation and iron metabolism were evaluated. Immunoprecipitation, protein degradation and ubiquitination assays were performed to demonstrate the regulation of TRIM7 on its candidate proteins.

Results

TRIM7 expression was elevated in human glioblastoma cells and tissues. TRIM7 silence suppressed growth and induced death, while TRIM7 overexpression facilitated growth and inhibited death of human glioblastoma cells. Meanwhile, TRIM7-silenced cells exhibited increased iron accumulation, lipid peroxidation and ferroptosis, which were significantly reduced by TRIM7 overexpression. Mechanistically, TRIM7 directly bound to and ubiquitinated nuclear receptor coactivator 4 (NCOA4) using K48-linked chains, thereby reducing NCOA4-mediated ferritinophagy and ferroptosis of human glioblastoma cells. Moreover, we found that TRIM7 deletion sensitized human glioblastoma cells to temozolomide therapy.

Conclusion

We for the first time demonstrate that TRIM7 modulates NCOA4-mediated ferritinophagy and ferroptosis in glioblastoma cells, and our findings provide a novel insight into the progression and treatment for human glioblastoma.

Comprehensive Analysis of the Expression and Prognosis for Tripartite Motif-Containing Genes in Breast Cancer

Tripartite motif-containing genes (TRIMs), with a ubiquitin ligase’s function, play critical roles in antitumor immunity by activating tumor-specific immune responses and stimulating tumor proliferation, thus affecting patient outcomes. However, the expression pattern and prognostic values of TRIMs in breast cancer (BC) are not well clarified. In this study, several datasets and software were integrated to perform a comprehensive analysis of the expression pattern in TRIMs and investigate their prognosis values in BC. We found that TRIM59/46 were significantly upregulated and TRIM66/52-AS1/68/7/2/9/29 were decreased in BC and validated them using an independent cohort. The expression of numerous TRIMs are significantly correlated with BC molecular subtypes, but not with tumor stages or patient age at diagnosis. Higher expression of TRIM3/14/69/45 and lower expressions of TRIM68/2 were associated with better overall survival in BC using the Kaplan–Meier analysis. The multivariate Cox proportional hazards model identified TRIM45 as an independent prognostic marker. Further analysis of single-cell RNA-seq data revealed that most TRIMs are also expressed in nontumor cells. Higher expression of some TRIMs in the immune or stromal cells suggests an important role of TRIMs in the BC microenvironment. Functional enrichment of the co-expression genes indicates that they may be involved in muscle contraction and interferon-gamma signaling pathways. In brief, through the analysis, we provided several TRIMs that may contribute to the tumor progression and TRIM45 as a potential new prognostic biomarker for BC.

TRIM3 facilitates estrogen signaling and modulates breast cancer cell progression

BACKGROUND

Breast cancer is the most common cancer in women worldwide. More than 70% of breast cancers are estrogen receptor (ER) alpha positive. Compared with ER alpha-negative breast cancer, which is more aggressive and has a shorter survival time, ER alpha-positive breast cancer could benefit from endocrine therapy. Selective estrogen receptor modulators, such as tamoxifen, are widely used in endocrine therapy. Approximately half of ER alpha-positive breast cancer patients will eventually develop endocrine resistance, making it a major clinical challenge in therapy. Thus, decoding the throughput of estrogen signaling, including the control of ER alpha expression and stability, is critical for the improvement of breast cancer therapeutics.

METHODS

TRIM3 and ER alpha protein expression levels were measured by western blotting, while the mRNA levels of ER alpha target genes were measured by RT-PCR. A CCK-8 assay was used to measure cell viability. RNA sequencing data were analyzed by Ingenuity Pathway Analysis. Identification of ER alpha signaling activity was accomplished with luciferase assays, RT-PCR and western blotting. Protein stability assays and ubiquitin assays were used to detect ER alpha protein degradation. Ubiquitin-based immunoprecipitation assays were used to detect the specific ubiquitination modification on the ER alpha protein.

RESULTS

In our current study, we found that TRIM3, an E3 ligase, can promote ER alpha signaling activity and breast cancer progression. TRIM3 depletion inhibits breast cancer cell proliferation and migration, while unbiased RNA sequencing data indicated that TRIM3 is required for the activity of estrogen signaling on the -genome-wide scale. The immunoprecipitation assays indicated that TRIM3 associates with ER alpha and promotes its stability, possibly by inducing K63-linked polyubiquitination of ER alpha. In conclusion, our data implicate a nongenomic mechanism by which TRIM3 stabilizes the ER alpha protein to control ER alpha target gene expression linked to breast cancer progression.

CONCLUSION

Our study provides a novel posttranslational mechanism in estrogen signaling. Modulation of TRIM3 expression or function could be an interesting approach for breast cancer treatment. Video abstract.

[TRIM21 suppresses invasion of hepatocellular carcinoma cells by promoting β-catenin ubiquitylation and degradation]

OBJECTIVE

To explore the role of TRIM21 in modulating the invasive phenotype of hepatocellular carcinoma (HCC) cells and its mechanism of action.

METHODS

RNA interference technique was used to knock down the expression of TRIM21 and β-catenin, alone or in combination, in HCC cell lines 97H and LM3, and the interfering efficiency and the activity of closely related pathways were determined using Western blotting. The two cells with TRIM21 knockdown (siTRIM21 97H and siTRIM21 LM3 cells) were assessed for their invasion ability in vitro using Transwell invasion assay, and the lung metastasis capacity of siTRIM21 LM3 cells following tail vein injection was evaluated in nude mice. The binding of TRIM21 with β-catenin and the ubiquitylation level of β-catenin in TRIM21-overexpressing HEK293 cells were determined with Western blotting and co-immunoprecipitation assay. We also compared the overall survival of patients with CTNNB1^highTRIM21^high and CTNNB1^highTRIM21^low HCC subtypes using Kaplan-Meier method based on filtrated and grouped HCC clinical data from TCGA database.

RESULTS

TRIM21 knockdown significantly enhanced the invasion ability of 97H and LM3 cells in vitro (P < 0.01 or 0.05) and the lung metastasis ability of LM3 cells in nude mice (P < 0.01), and simultaneous knockdown of β -catenin obviously suppressed the in vitro invasiveness of the cells (P < 0.0001 or 0.05). Co-immunoprecipitation assay showed that TRIM21 was capable of directly binding with β-catenin protein to accelerate the ubiquitination and degradation of the latter, leading to inhibition of nuclear translocation of β-catenin and hence reduced invasiveness of HCC cells. Bioinformatic analysis showed that compared patients with CTNNB1^highTRIM21^low HCC subtype where Wnt pathway was activated, the patients with CTNNB1^highTRIM21^high HCC subtype had a significantly better survival outcomes (P < 0.05).

CONCLUSION

A high expression of TRIM21 suppresses the invasion of HCC cells by promoting β-catenin ubiquitylation and degradation, which possibly explains the poor prognosis of CTNNB1^highTRIM21^low HCC patients.

Tripartite Motif Containing 3 inhibits the aggressive behaviors of papillary thyroid carcinoma and indicates lower recurrence risk

BACKGROUND

Tripartite Motif Containing 3 (TRIM3) has been reported to be downregulated in several malignancies. However, its prognostic significance in thyroid cancer remains unknown.

OBJECTIVE

Here we aimed to investigate TRIM3's expression and its involvement in papillary thyroid carcinoma (PTC).

METHODS

Clinicopathological analyses were performed in patients with PTC. Expression of TRIM3 protein was evaluated by IHC. The prognostic role of TRIM3 in PTC patients was assessed by univariate and multivariate analyses. Cell proliferation and invasion were tested in two PTC cell lines following overexpression or knockdown.

RESULTS

TRIM3 was decreased in PTC tissues compared to adjacent thyroid tissues on both mRNA and protein levels. Additionally, low expression of TRIM3 was significantly related to tumor size, lymph node metastasis and TNM stage. Moreover, TRIM3 was identified as an independent prognosis factor by multivariate analysis. Cellular data revealed that TRIM3 can inhibit the proliferation and invasion of PTC cells. Consistently, TRIM3 can upregulate the expression level of E-cadherin, while downregulate N-cadherin, Vimentin, and cyclin D1 expression.

CONCLUSIONS

TRIM3 expression was downregulated in PTC tissues comparing with that in adjacent nontumorous thyroid tissues. Lower TRIM3 expression in PTC can contribute independently to a poorer prognosis by enhancing PTC proliferation and invasion, highlighting its potential as a novel therapeutic target and prognostic biomarker.

Tripartite motif-containing 3 (TRIM3) enhances ER signaling and confers tamoxifen resistance in breast cancer

Tamoxifen resistance remains a clinical problem in estrogen receptor (ER)-positive breast cancer. SUMOylation of ERα enhances ERα-induced transcription activity. Tripartite motif-containing (TRIM) proteins are a new class of SUMO E3 ligases, which regulate the SUMOylation of proteins. However, the precise molecular mechanism and function of TRIM3 in SUMOylation and the response to tamoxifen remain unclear. In the present study, we observed that TRIM3 was dramatically overexpressed in breast cancer, which correlated with tamoxifen resistance. Furthermore, TRIM3 overexpression significantly correlated with poor survival of patients with ER⁺ breast cancer treated with tamoxifen. TRIM3 overexpression conferred cell survival and tumorigenesis, whereas knocking down of TRIM3 reduced these capabilities. Moreover, TRIM3, as a ubiquitin carrier protein 9 (UBC9) binding protein, promoted SUMO modification of estrogen receptor 1 (ESR1) and activated the ER pathway. Silencing UBC9 abolished the function of TRIM3 in regulating tamoxifen resistance. These results suggest TRIM3 as a novel biomarker for breast cancer therapy, indicating that inhibiting TRIM3 combined with tamoxifen might provide a potential treatment for breast cancer.

The translational values of TRIM family in pan-cancers: From functions and mechanisms to clinics

Cancer is the second leading cause of human death across the world. Tripartite motif (TRIM) family, with E3 ubiquitin ligase activities in majority of its members, is reported to be involved in multiple cellular processes and signaling pathways. TRIM proteins have critical effects in the regulation of biological behaviors of cancer cells. Here, we discussed the current understanding of the molecular mechanism of TRIM proteins regulation of cancer cells. We also comprehensively reviewed published studies on TRIM family members as oncogenes or tumor suppressors in the oncogenesis, development, and progression of a variety of types of human cancers. Finally, we highlighted that certain TRIM family members are potential molecular biomarkers for cancer diagnosis and prognosis, and potential therapeutic targets.

Decreased expression of TRIM3 gene predicts a poor prognosis in gastric cancer

BACKGROUND/AIMS

Tripartite motif-containing 3 (TRIM3) is a member of the TRIM protein family which is known to be involved in development of numerous tumor types. However, the prognostic role of TRIM3 in gastric cancer (GC) remained to be clarified. The aim of this study was to evaluate the expression pattern and prognostic significance of TRIM3 gene and its relationship with β-catenin, CyclinD, and BCL2 expression in patients with GC.

METHODS

A total of 40 fresh primary gastric cancer tumors and their matched adjacent noncancerous tissues were selected from the First Affiliated Hospital of Mashhad University. Real-time quantitative RT-PCR was performed to evaluate differences in TRIM3 expression in GC and normal tissues. The correlation between TRIM3 expression level and patients' overall survival, some clinicopathological variables, and β-catenin, CyclinD, and BCL-2 genes expression level were also studied. Moreover, patients were divided in two groups according to the TRIM3 expression levels: low and high.

RESULTS

Compared to noncancerous tissues, TRIM3 expression in GC tissues was significantly increased (fold change = 1.58). Kaplan-Meier survival analysis revealed a significant difference of patient survival according to TRIM3 expression status (P = 0.012). Low TRIM3 expression was associated with shorter overall survival and was an independent predictor for poor prognosis in GC patients (HR, 1.25; 95%CI, 1.02-1.60; P = 0.045). Expression of TRIM3 was negatively correlated with expression of β-catenin, BCL-2, and CyclinD as genes for proliferation, apoptosis, and the cell cycle in GC patients.

CONCLUSIONS

This study demonstrates that decreased level of TRIM3 mRNA expression is associated with poor prognosis in patients with gastric cancer. TRIM3 may play a protective role in gastric cancer by relieving the effects of cancer progressive genes and could be considered for further investigations as a prognostic biomarker.

TRIM3 attenuates apoptosis in Parkinson's disease via activating PI3K/AKT signal pathway

This article aims to study tripartite motif-containing protein 3 (TRIM3) effects on Parkinson's disease (PD). TRIM3 expression in venous blood of PD patients was detected by qRT-PCR. PD mouse model and PD SH-SY5Y cell model were constructed. PD cells were treated by LY294002 (a PI3K inhibitor). The apoptosis of PD mouse midbrain was detected. Glutathione (GSH) and superoxide dismutase (SOD) level in PD cells and mice midbrain was analyzed. Intracellular reactive oxygen species (ROS) and MMP were detected. The effect of TRIM3 on cell viability, apoptosis and PI3K/AKT signal pathway were analyzed. As a result, TRIM3 expression in venous blood of PD patients was decreased. TRIM3 up-regulation in PD mouse decreased midbrain tissues apoptosis. TRIM3 up-regulation increased GSH and SOD levels in PD mice midbrain tissues and PD cells. TRIM3 up-regulation in PD cells prominently reduced ROS and MMP. TRIM3 up-regulation increased PD cells viability and decreased apoptosis. TRIM3 up-regulation in PD cells elevated Bcl-2 protein expression and weakened Bax, Cleaved-caspase 3 and Cleaved-caspase 9 proteins expression. TRIM3 up-regulation increased p-PI3K/PI3K and p-AKT/AKT ratio. PI3K inhibitor treatment reversed the inhibitory effect of TRIM3 up-regulation on PD cells apoptosis. Thus, TRIM3 might attenuate apoptosis in PD via activating PI3K/AKT signal pathway.

Role of nuclear-cytoplasmic protein localization during Drosophila neuroblast development

Nuclear-cytoplasmic localization is an efficient way to regulate transcription factors and chromatin remodelers. Altering the location of existing protein pools also facilitates a more rapid response to changes in cell activity or extracellular signals. There are several examples of proteins that are regulated by nucleo-cytoplasmic shuttling, which are required for Drosophila neuroblast development. Disruption of the localization of homologs of these proteins has also been linked to several neurodegenerative disorders in humans. Drosophila has been used extensively to model the neurodegenerative disorders caused by aberrant nucleo-cytoplasmic localization. Here, we focus on the role of alternative nucleo-cytoplasmic protein localization in regulating proliferation and cell fate decisions in the Drosophila neuroblast and in neurodegenerative disorders. We also explore the analogous role of RNA binding proteins and mRNA localization in the context of regulation of nucleo-cytoplasmic localization during neural development and a role in neurodegenerative disorders.

TRIM11 facilitates chemoresistance in nasopharyngeal carcinoma by activating the β-catenin/ABCC9 axis via p62-selective autophagic degradation of Daple

Chemotherapy resistance is the major cause of nasopharyngeal carcinoma (NPC) treatment failure. Tripartite motif-containing protein (TRIM) family members play important roles in tumor development and chemotherapy failure. Here, based on a screening analysis of 71 TRIM family members by qRT-PCR, we first confirmed that the TRIM11 levels were significantly higher in drug-resistant NPC cells than in non-drug-resistant NPC cells, and high TRIM11 expression predicted poor overall survival (OS) and progression-free survival (PFS). N(6)-Methyladenosine (m6A) was highly enriched in TRIM11 in NPC drug-resistant cells and enhanced its RNA stability. TRIM11 enhanced the multidrug resistance in NPC by inhibiting apoptosis in vitro and promoting cisplatin (DDP) resistance in vivo. TRIM11 associated with Daple and promoted Daple ubiquitin-mediated degradation in a p62-selective autophagic manner, further upregulating β-catenin expression to induce ABCC9 expression by directly binding to the ABCC9 promoter. TRIM11 may regulate NPC drug resistance by positively modulating the Daple/β-catenin/ABCC9 signaling pathway. Thus, TRIM11 may be a potential diagnostic marker and therapeutic target for chemoresistant NPC.

miR-4513 promotes breast cancer progression through targeting TRIM3

The biological function of microRNA-4513 (miR-4513) in human cancers is emerging. However, it remains unknown whether miR-4513 has a role in breast cancer (BC). In this study, we analyzed the expression of miR-4513 and tripartite motif containing 3 (TRIM3) in BC cell lines. The biological roles of miR-4513 and TRIM3 in BC were analyzed by cell counting kit-8 assay, colony formation assay, wound healing assay, and transwell invasion assay. The effects of miR-4513 or TRIM3 expression on the overall survival of BC patients were analyzed at Kaplan-Meier plotter website. We found miR-4513 expression was upregulated, whereas TRIM3 expression was downregulated in BC cell lines. Importantly, high miR-4513 or low TRIM3 expression was revealed as predictors for poorer overall survival of BC patients. Luciferase activity assay and western blot assay revealed TRIM3 was a direct target of miR-4513. Moreover, we showed miR-4513 was able to regulate BC cell proliferation, colony formation, cell migration, and cell invasion through regulating TRIM3. Taken together, our results suggested miR-4513 functions as an oncogene in the progression of BC and, therefore, miR-4513 may be validated as a potential therapeutic target in the future.

Targeting Chemoresistant Tumors: Could TRIM Proteins-p53 Axis Be a Possible Answer?

Chemosensitivity is a crucial feature for all tumours so that they can be successfully treated, but the huge heterogeneity of these diseases, to be intended both inter- and intra-tumour, makes it a hard-to-win battle. Indeed, this genotypic and phenotypic variety, together with the adaptability of tumours, results in a plethora of chemoresistance acquisition mechanisms strongly affecting the effectiveness of treatments at different levels. Tripartite motif (TRIM) proteins are shown to be involved in some of these mechanisms thanks to their E3-ubiquitin ligase activity, but also to other activities they can exert in several cellular pathways. Undoubtedly, the ability to regulate the stability and activity of the p53 tumour suppressor protein, shared by many of the TRIMs, represents the preeminent link between this protein family and chemoresistance. Indeed, they can modulate p53 degradation, localization and subset of transactivated target genes, shifting the cellular response towards a cytoprotective or cytotoxic reaction to whatever damage induced by therapy, sometimes in a cellular-dependent way. The involvement in other chemoresistance acquisition mechanisms, independent by p53, is known, affecting pivotal processes like PI3K/Akt/NF-κB signalling transduction or Wnt/beta catenin pathway, to name a few. Hence, the inhibition or the enhancement of TRIM proteins functionality could be worth investigating to better understand chemoresistance and as a strategy to increase effectiveness of anticancer therapies.

TRIM2 downregulation in clear cell renal cell carcinoma affects cell proliferation, migration, and invasion and predicts poor patients' survival

Background and aim

Tripartite motif containing (TRIM) family protein has been involved in multiple pathogenesis of cancers. TRIM2 is a member of the family, and its role in clear cell renal cell carcinoma (ccRCC) remains to be unclarifid. Here, we showed the clinical value and biological role of TRIM2 in ccRCC.

Methods

ROC curves analyzed the clinicopathological parameters, Kaplan-Meier survival analysis determined the correlation of OS and DFS time, multivariate analysis demonstrated the prognostic indicator in overall survival and disease-free survival of ccRCC with TRIM2 expression in The Cancer Genome Atlas Kidney Clear Cell Carcinoma (TCGA-KIRC) database. Western blotting and immunohistochemistry were used to check the level of TRIM2 expression. Gain-of-function assay by exogenous overexpression of TRIM2 studied the biological role of TRIM2 in renal cell carcinoma cells.

Results

TRIM2 expression was associated with various clinicopathologicalfactors and lower TRIM2 expression was interrelated to a poor prognosis. The levels of TRIM2 expression were also scanty in ccRCC tissues and renal cancer cell lines than in normal control. The biological role of TRIM2 in ccRCC was identifid by bioinformatics analysis and functional analysis. Exogenous overexpression of TRIM2 with the gain-of-function assay in renal cell carcinoma cells showed that the cell proliferation, migration, and invasion were signifiantly suppressed.

Conclusion

These results showed that TRIM2 acted as an antitumor gene and a specifi prognostic indicator for patients with ccRCC, which indicated that positive modulation of TRIM2 might be a novel treatment strategy for ccRCC.

TRIM59 promotes breast cancer motility by suppressing p62-selective autophagic degradation of PDCD10

Cancer cells adopt various modes of migration during metastasis. How the ubiquitination machinery contributes to cancer cell motility remains underexplored. Here, we report that tripartite motif (TRIM) 59 is frequently up-regulated in metastatic breast cancer, which is correlated with advanced clinical stages and reduced survival among breast cancer patients. TRIM59 knockdown (KD) promoted apoptosis and inhibited tumor growth, while TRIM59 overexpression led to the opposite effects. Importantly, we uncovered TRIM59 as a key regulator of cell contractility and adhesion to control the plasticity of metastatic tumor cells. At the molecular level, we identified programmed cell death protein 10 (PDCD10) as a target of TRIM59. TRIM59 stabilized PDCD10 by suppressing RING finger and transmembrane domain-containing protein 1 (RNFT1)-induced lysine 63 (K63) ubiquitination and subsequent phosphotyrosine-independent ligand for the Lck SH2 domain of 62 kDa (p62)-selective autophagic degradation. TRIM59 promoted PDCD10-mediated suppression of Ras homolog family member A (RhoA)-Rho-associated coiled-coil kinase (ROCK) 1 signaling to control the transition between amoeboid and mesenchymal invasiveness. PDCD10 overexpression or administration of a ROCK inhibitor reversed TRIM59 loss-induced contractile phenotypes, thereby accelerating cell migration, invasion, and tumor formation. These findings establish the rationale for targeting deregulated TRIM59/PDCD10 to treat breast cancer.

Elevated TRIM23 expression predicts poor prognosis in Chinese gastric cancer

The gene TRIM23 (tripartite motif containing 23) is a member of the tripartite motif (TRIM) family whose expression putatively participates in many pathophysiological processes. Nonetheless, the role of TRIM23 in gastric cancer (GC) remains uncertain. Our study evaluated the expression of TRIM23 in GC tissues and cell lines, and investigated an association between TRIM23 and survival. In the present study, our results demonstrated that TRIM23 mRNA and protein were frequently over-expressed in GC cell lines and GC tissues. High level of TRIM23 protein correlated with tumor size, tumor-node-metastasis (TNM) stage, depth of invasion, lymph node metastasis (LNM), tumor differentiation, and nerve invasion. Compared with the low TRIM23 protein group, the high TRIM23 protein group was significantly associated with worse prognosis of GC patients. Consistently, the KM-plot database suggested that high TRIM23 mRNA expression was also linked to a poor prognosis in GC patients both in positive and negative subgroups of human epidermal growth factor receptor 2 (HER2). But in the HER2 positive subgroup, the advantages of the low TRIM23 expression on overall survival were much more statistically significant. The univariate analysis indicated that TRIM23 expression correlated with overall survival. The multivariate analysis showed that independent factors of prognosis in GC were lymph node metastasis, vascular invasion, and depth of invasion. In summary, TRIM23 may be associated with progression of GC, and may be considered a therapeutic target for GC patients.

Exosomal TRIM3 is a novel marker and therapy target for gastric cancer

Background

Exosomes are critically involved in cancer development and progression. The exosomal contents have been suggested as ideal cancer biomarkers. In this study, we investigated the expression of exosomal proteins in the serum of gastric cancer patients and their roles in gastric cancer.

Methods

The proteomic profile of exosomes from the serum of gastric cancer patients was detected by using LC-MS/MS. The expression of TRIM3 in exosomes from the serum of gastric cancer patients and healthy controls was assessed by ELISA and western blot. Immunohistochemistry was used to detect TRIM3 expression in gastric cancer tissues and their matching adjacent tissues. The growth and migration abilities of gastric cancer cells with TRIM3 overexpression or knockdown in vitro were evaluated by colony formation assay and transwell migration assay. The effects of TRIM3 overexpression or knockdown on gastric cancer growth and metastasis in vivo were investigated by using subcutaneous xenograft tumor and peritoneal metastasis mouse model. The effects of TRIM3-overexpressing exosomes on gastric cancer growth and metastasis in vitro and in vivo were also evaluated.

Results

We found that the expression levels of TRIM3 mRNA and protein were decreased in gastric cancer tissues compared to the matched control tissues. In addition, the levels of TRIM3 protein in the serum exosomes of gastric cancer patients were lower than that in healthy controls. We demonstrated that TRIM3 overexpression reduced while TRIM3 knockdown promoted the growth and metastasis of gastric cancer in vitro and in vivo through the regulation of stem cell factors and EMT regulators. Moreover, exosomes-mediated delivery of TRIM3 protein could suppress gastric cancer growth and metastasis in vitro and in vivo.

Conclusions

Taken together, our findings suggest that exosomal TRIM3 may serve as a biomarker for gastric cancer diagnosis and the delivery of TRIM3 by exosomes may provide a new avenue for gastric cancer therapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0825-0) contains supplementary material, which is available to authorized users.

A regulatory mutant on TRIM26 conferring the risk of nasopharyngeal carcinoma by inducing low immune response

The major histocompatibility complex (MHC) is most closely associated with nasopharyngeal carcinoma (NPC), but the complexity of its genome structure has proven challenging for the discovery of causal MHC loci or genes. We conducted a targeted MHC sequencing in 40 Cantonese NPC patients followed by a two‐stage replication in 1065 NPC cases and 2137 controls of Southern Chinese descendent. Quantitative RT‐PCR analysis (qRT‐PCR) was used to detect gene expression status in 108 NPC and 43 noncancerous nasopharyngeal (NP) samples. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) were used to assess the transcription factor binding site. We discovered that a novel SNP rs117565607_A at TRIM26 displayed the strongest association (OR = 1.909, Pcombined = 2.750 × 10⁻¹⁹). We also observed that TRIM26 was significantly downregulated in NPC tissue samples with genotype AA/AT than TT. Immunohistochemistry (IHC) test also found the TRIM26 protein expression in NPC tissue samples with the genotype AA/AT was lower than TT. According to computational prediction, rs117565607 locus was a binding site for the transcription factor Yin Yang 1 (YY1). We observed that the luciferase activity of YY1 which is binding to the A allele of rs117565607 was suppressed. ChIP data showed that YY1 was binding with T not A allele. Significance analysis of microarray suggested that TRIM26 downregulation was related to low immune response in NPC. We have identified a novel gene TRIM26 and a novel SNP rs117565607_A associated with NPC risk by regulating transcriptional process and established a new functional link between TRIM26 downregulation and low immune response in NPC.

TRIM11, a direct target of miR-24-3p, promotes cell proliferation and inhibits apoptosis in colon cancer

TRIM11 (tripartite motif-containing protein 11) is an E3 ubiquitin ligase recently identified as an oncogene in malignant glioma and lung cancer. In the present study, we report that expression of TRIM11 was increased in colon cancer (CC) tissue relative to paired normal tissues and that higher TRIM11 levels predicted poor overall survival (OS) and disease-free survival (DFS) in CC patients. Mechanistically, we showed that miR-24-3p downregulation contributes to TRIM11 upregulation in CC. We also demonstrated that TRIM11 overexpression promotes cell proliferation and colony formation and inhibits apoptosis in CC, while knocking down TRIM11 using CRISPR/Cas9-mediated genome editing inhibited cell proliferation and induced apoptosis. Silencing TRIM11 in vivo decreased tumor growth. These findings indicate that TRIM11 facilitates CC progression by promoting cell proliferation and inhibiting apoptosis and that the novel miR-24-3p/TRIM11 axis may be a useful new target for treating patients with CC.

Tripartite motif-containing 3 (TRIM3) inhibits tumor growth and metastasis of liver cancer

BACKGROUND

Reduced expression of tripartite motif-containing 3 (TRIM3) has been reported to be involved in the pathogenesis of human glioblastoma. In our previous research, we found that TRIM3 expression was markedly reduced in human primary hepatocellular carcinoma (HCC) tissues and that low TRIM3 expression was associated with short survival of HCC patients. However, the role of TRIM3 in liver cancer remains unknown. This study aimed to investigate the function of TRIM3 in liver cancer cells.

METHODS

The protein levels of TRIM3 in five liver cancer cell lines (SK-Hep1, Hep3B, Huh7, HepG2, Bel-7402) and one normal liver cell line (L02) were detected with Western blotting. HepG2 and Bel-7402 cells with low TRIM3 expression were infected with recombinant lentiviruses overexpressing TRIM3 (LV-TRIM3), whereas Huh7 and Hep3B cells with high TRIM3 expression were transfected with TRIM3-targeted small interfering RNA (siTRIM3). The functions of TRIM3 in the proliferation, colony formation, cell cycle, migration, invasion, and apoptosis of the above cell lines were examined. The effect of TRIM3 on tumor growth and metastases in nude mice was also investigated.

RESULTS

TRIM3 was overexpressed in HepG2 and Bel-7402 cells with LV-TRIM3 infection, which further reduced proliferation, colony formation, migration, and invasion of both cell lines. Cell cycle analysis showed that TRIM3 overexpression induced G₀/G₁ phase arrest in HepG2 and Bel-7402 cells. Moreover, apoptosis was not increased in HepG2 or Bel-7402 cells overexpressing TRIM3. Contrarily, silencing TRIM3 expression in Huh7 and Hep3B cells by siTRIM3 led to significantly decreased percentages of both cells in the G₀/G₁ phase and promoted cell proliferation, colony formation, migration, and invasion. In vivo experiment results confirmed that TRIM3 overexpression suppressed tumor growth and metastasis.

CONCLUSIONS

TRIM3 plays a tumor-suppressing role in the regulation of liver cancer development by reducing cell proliferation through cell cycle arrest at the G₀/G₁ phase.

Bioinformatics analysis of the prognostic value of Tripartite Motif 28 in breast cancer

Tripartite motif containing 28 (TRIM28) is a transcriptional regulator acting as an essential corepressor for Krüppel-associated box zinc finger domain-containing proteins in multiple tissue and cell types. An increasing number of studies have investigated the function of TRIM28; however, its prognostic value in breast cancer (BC) remains unclear. In the present study, the expression of TRIM28 was identified to be significantly higher in cancerous compared with healthy tissue samples. Furthermore, it was demonstrated that TRIM28 expression was significantly correlated with several clinicopathological characteristics of patients with BC, such as p53 mutation, tumor recurrence and Elston grade of the tumor. In addition, a protein-protein interaction network was created to illustrate the interactions of TRIM28 with other proteins. The prognostic value of TRIM28 in patients with BC was investigated using the Kaplan-Meier Plotter database, which revealed that high expression of TRIM28 is a predictor of poor prognosis in patients with BC. In conclusion, the results of the present study indicate that TRIM28 provides a survival advantage to patients with BC and is a novel prognostic biomarker, in addition to being a therapeutic target for the treatment of BC.

The tripartite motif-containing protein 3 on the proliferation and cytokine secretion of rheumatoid arthritis fibroblast-like synoviocytes

Recent studies have revealed fibroblast-like synoviocytes (FLS) as a pivotal effector cell in the inflamed joint of rheumatoid arthritis (RA) patients. FLS exhibit high proliferation rates and constitutive expression of cytokines, contributing to the pathogenesis of RA. In this study, we found that the expression of tripartite motif-containing protein 3 (TRIM3), a candidate tumor suppressor gene, was lower in synovial tissue samples of RA patients than in that of healthy controls. We then investigated the role of TRIM3 on the proliferation and cytokine secretion of primary cultured FLS from RA patients. Enforced expression of TRIM3 in RA FLS led to significantly decreased cell proliferation as indicated by Cell Counting Kit-8 assay, reduced secretion of tumor necrosis factor-α (TNF)-α, interleukin (IL)-1β and IL-6 as indicated by enzyme-linked immunosorbent assays, and decreased p38 phosphorylation as assessed by western blot analysis. The proteins promoting cell cycles (cyclin D1 and PCNA) were downregulated and the protein negatively regulating cell cycle progression (p53 and p21) was upregulated after TRIM3 overexpression. Importantly, TRIM3 knockdown had reverse effects on cell proliferation, which was suppressed by the p38-specific inhibitor SB203580. In conclusion, the current results demonstrated the downregulation of TRIM3 expression in RA synovial tissues. Importantly, TRIM3 exerted an anti-proliferation role in RA FLS via p38 signaling pathway.

Molecular Programs Underlying Asymmetric Stem Cell Division and Their Disruption in Malignancy

Asymmetric division of stem cells is a highly conserved and tightly regulated process by which a single stem cell produces two unequal daughter cells. One retains its stem cell identity while the other becomes specialized through a differentiation program and loses stem cell properties. Coordinating these events requires control over numerous intra- and extracellular biological processes and signaling networks. In the initial stages, critical events include the compartmentalization of fate determining proteins within the mother cell and their subsequent passage to the appropriate daughter cell in order to direct their destiny. Disturbance of these events results in an altered dynamic of self-renewing and differentiation within the cell population, which is highly relevant to the growth and progression of cancer. Other critical events include proper asymmetric spindle assembly, extrinsic regulation through micro-environmental cues, and non-canonical signaling networks that impact cell division and fate determination. In this review, we discuss mechanisms that maintain the delicate balance of asymmetric cell division in normal tissues and describe the current understanding how some of these mechanisms are deregulated in cancer.

Potential role of TRIM3 as a novel tumour suppressor in colorectal cancer (CRC) development

OBJECTIVE

Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in the United States. Recent cancer genome-sequencing efforts and complementary functional studies have led to the identification of a collection of candidate 'driver' genes involved in CRC tumorigenesis. Tripartite motif (TRIM3) is recently identified as a tumour suppressor in glioblastoma but this tumour-suppressive function has not been investigated in CRC.

MATERIAL AND METHODS

In this study, we investigated the potential role of TRIM3 as a tumour suppressor in CRC development by manipulating the expression of TRIM3 in two authentic CRC cell lines, HCT116 and DLD1, followed by various functional assays, including cell proliferation, colony formation, scratch wound healing, soft agar, and invasion assays. Xenograft experiment was performed to examine in vivo tumour-suppressive properties of TRIM3.

RESULTS

Small-interfering RNA (siRNA) mediated knockdown of TRIM3 conferred growth advantage in CRC cells. In contrast, overexpression of TRIM3 affected cell survival, cell migration, anchorage independent growth and invasive potential in CRC cells. In addition, TRIM3 was found to be down-regulated in human colon cancer tissues compared with matched normal colon tissues. Overexpression of TRIM3 significantly inhibited tumour growth in vivo using xenograft mouse models. Mechanistic investigation revealed that TRIM3 can regulate p53 protein level through its stabilisation.

CONCLUSIONS

TRIM3 functions as a tumour suppressor in CRC progression. This tumour-suppressive function is exerted partially through regulation of p53 protein. Therefore, this protein may represent a novel therapeutic target for prevention or intervention of CRC.

Drosophila Brat and Human Ortholog TRIM3 Maintain Stem Cell Equilibrium and Suppress Brain Tumorigenesis by Attenuating Notch Nuclear Transport

Cancer stem cells exert enormous influence on neoplastic behavior, in part by governing asymmetric cell division and the balance between self-renewal and multipotent differentiation. Growth is favored by deregulated stem cell division, which enhances the self-renewing population and diminishes the differentiation program. Mutation of a single gene in Drosophila, Brain Tumor (Brat), leads to disrupted asymmetric cell division resulting in dramatic neoplastic proliferation of neuroblasts and massive larval brain overgrowth. To uncover the mechanisms relevant to deregulated cell division in human glioma stem cells, we first developed a novel adult Drosophila brain tumor model using brat-RNAi driven by the neuroblast-specific promoter inscuteable Suppressing Brat in this population led to the accumulation of actively proliferating neuroblasts and a lethal brain tumor phenotype. brat-RNAi caused upregulation of Notch signaling, a node critical for self-renewal, by increasing protein expression and enhancing nuclear transport of Notch intracellular domain (NICD). In human glioblastoma, we demonstrated that the human ortholog of Drosophila Brat, tripartite motif-containing protein 3 (TRIM3), similarly suppressed NOTCH1 signaling and markedly attenuated the stem cell component. We also found that TRIM3 suppressed nuclear transport of active NOTCH1 (NICD) in glioblastoma and demonstrated that these effects are mediated by direct binding of TRIM3 to the Importin complex. Together, our results support a novel role for Brat/TRIM3 in maintaining stem cell equilibrium and suppressing tumor growth by regulating NICD nuclear transport. Cancer Res; 76(8); 2443-52. ©2016 AACR.

TRIM-NHL proteins in development and disease

TRIM-NHL proteins are key regulators of developmental transitions, for example promoting differentiation, while inhibiting cell growth and proliferation, in stem and progenitor cells. Abnormalities in these proteins have been also associated with human diseases, particularly affecting muscular and neuronal functions, making them potential targets for therapeutic intervention. The purpose of this review is to provide a systematic and comprehensive summary on the most studied TRIM-NHL proteins, highlighting examples where connections were established between structural features, molecular functions and biological outcomes.

Downregulation of TRIM21 contributes to hepatocellular carcinoma carcinogenesis and indicates poor prognosis of cancers

The aim of our work is to clarify the clinical implication and functional role of tripartite motif 21 (TRIM21) in hepatocellular carcinoma (HCC). We validated that TRIM21 was downregulated in liver cancer samples by immunohistochemical (IHC) staining. We also demonstrated that its downregulation was associated with several clinicopathologic features such as tumor numbers, T stage, Barcelona Clinic Liver Cancer (BCLC) stage, and Cancer of the Liver Italian Program (CLIP) stage of HCC patients. Importantly, the expression of TRIM21 in tumor samples is significantly correlated with the prognosis of the patients. We further silenced TRIM21 in HCC cell HepG2 and LM3 and confirmed that TRIM21 silencing will promote cancer cell proliferation (CCK-8 assay), colony forming (plate colony-forming assay), migration (transwell assay), and the ability of antiapoptosis (annexin V-FITC/PI staining) in vitro. Then, we predicted gene sets influenced by TRIM21 by using bioinformatic tools. For the first time, we prove that TRIM21 is a potential tumor suppressor in HCC and its low expression indicates poor prognosis. Our findings provide useful insight into the mechanism of HCC origin and progression and offer clues to novel HCC therapies.

TRIM26 functions as a novel tumor suppressor of hepatocellular carcinoma and its downregulation contributes to worse prognosis

Hepatocellular carcinoma (HCC) is the one of the most common malignancies worldwide and its prognosis is extremely poor. Tripartite motif (TRIM) proteins play crucial roles in cancer cell biology but the function of tripartite motif 26 (TRIM26) has not been investigated. We demonstrated that low expression level of TRIM26 in tumor samples was significantly correlated with worse prognosis in HCC patients. We also demonstrated its expression level was associated with several clinicopathologic features such as AFP level and T stage of HCC patients. Furthermore, we validated that TRIM26 was significantly downregulated in HCC tissue compared with normal liver tissue. To further clarify the functional role of TRIM26 in HCC, We confirmed that TRIM26 silencing can promote cancer cell proliferation, colony forming, migration and invasion in vitro with HCC cell lines HepG2 and Bel-7402. Then we utilized bioinformatic tool to predict gene influenced by TRIM26, showing TRIM26 could modulate gene sets about cancer cell metabolism. In conclusion, we proved that TRIM26 is a novel tumor suppressor modulating multiple metabolism-related pathways in HCC. To our best knowledge, this is the first study to investigate the function of TRIM26 in cancer biology. Our findings provide useful insight into the mechanism of HCC origin and progression. Moreover, TRIM26 may represent a novel therapeutic target for HCC.

Cancer stem cell division: when the rules of asymmetry are broken

Asymmetric division of stem cells is a highly conserved and tightly regulated process by which a single stem cell produces two daughter cells and simultaneously directs the differential fate of both: one retains its stem cell identity while the other becomes specialized and loses stem cell properties. Coordinating these events requires control over numerous intra- and extracellular biological processes and signaling networks. In the initial stages, critical events include the compartmentalization of fate determining proteins within the mother cell and their subsequent passage to the appropriate daughter cell. Disturbance of these events results in an altered dynamic of self-renewing and differentiation within the cell population, which is highly relevant to the growth and progression of cancer. Other critical events include proper asymmetric spindle assembly, extrinsic regulation through micro-environmental cues, and noncanonical signaling networks that impact cell division and fate determination. In this review, we discuss mechanisms that maintain the delicate balance of asymmetric cell division in normal tissues and describe the current understanding how some of these mechanisms are deregulated in cancer. The universe is asymmetric and I am persuaded that life, as it is known to us, is a direct result of the asymmetry of the universe or of its indirect consequences. The universe is asymmetric. -Louis Pasteur.

The TRIM-NHL protein LIN-41 controls the onset of developmental plasticity in Caenorhabditis elegans

The mechanisms controlling cell fate determination and reprogramming are fundamental for development. A profound reprogramming, allowing the production of pluripotent cells in early embryos, takes place during the oocyte-to-embryo transition. To understand how the oocyte reprogramming potential is controlled, we sought Caenorhabditis elegans mutants in which embryonic transcription is initiated precociously in germ cells. This screen identified LIN-41, a TRIM-NHL protein and a component of the somatic heterochronic pathway, as a temporal regulator of pluripotency in the germline. We found that LIN-41 is expressed in the cytoplasm of developing oocytes, which, in lin-41 mutants, acquire pluripotent characteristics of embryonic cells and form teratomas. To understand LIN-41 function in the germline, we conducted structure-function studies. In contrast to other TRIM-NHL proteins, we found that LIN-41 is unlikely to function as an E3 ubiquitin ligase. Similar to other TRIM-NHL proteins, the somatic function of LIN-41 is thought to involve mRNA regulation. Surprisingly, we found that mutations predicted to disrupt the association of LIN-41 with mRNA, which otherwise compromise LIN-41 function in the heterochronic pathway in the soma, have only minor effects in the germline. Similarly, LIN-41-mediated repression of a key somatic mRNA target is dispensable for the germline function. Thus, LIN-41 appears to function in the germline and the soma via different molecular mechanisms. These studies provide the first insight into the mechanism inhibiting the onset of embryonic differentiation in developing oocytes, which is required to ensure a successful transition between generations.

Reprogramming into a naïve, pluripotent state during the oocyte-to-embryo transition is directed by the oocyte cytoplasm. To understand how this reprogramming is controlled, we searched for C. elegans mutants in which the activation of embryonic genome, a landmark event demarcating the switch from a germline- to embryo-specific transcription, is initiated precociously in germ cells. This screen identified a novel function for LIN-41, a member of the TRIM-NHL protein family, in preventing a premature onset of embryonic-like differentiation and teratoma formation in developing oocytes, thus ensuring a successful passage between generations. This is the first example of such a regulator in cells that are poised for embryonic development. Interestingly, the majority of molecular “roadblocks” to reprograming that have been identified so far are epigenetic regulators. However, we propose that, at least in germ cells, LIN-41-like regulators may fulfill an analogous role in the cytoplasm, which has possible implications for the generation of human pluripotent stem cells.

Decreased expression of TRIM3 is associated with poor prognosis in patients with primary hepatocellular carcinoma

Tripartite motif-containing 3 (TRIM3) is a member of the tripartite motif (TRIM) protein family and is reported to be involved in the pathogenesis of various cancers. The role of TRIM3 in hepatocellular carcinoma (HCC) is unknown; thus, the goal of this study was to explore the expression level and prognostic value of TRIM3 in HCC. The expression level of TRIM3 in HCC surgically resected tumors and corresponding nontumorous samples was detected by real-time quantitative RT-PCR, Western blotting, and immunohistochemistry. The correlation between TRIM3 expression level and the clinicopathological features and prognosis of HCC patients was also analyzed. We observed that TRIM3 expression was remarkably decreased in tumor tissue samples from HCC patients, relative to matched nontumorous tissue samples, at the mRNA (p = 0.018) and protein level (p = 0.02). Similarly, immunohistochemical analysis showed that 53.4 % of samples had low TRIM3 protein expression. Clinicopathological analysis revealed that low TRIM3 expression was significantly correlated with tumor size (p = 0.034), histological grade (p < 0.001), serum AFP (p = 0.025), and TNM stage (p = 0.021). Furthermore, Kaplan-Meier survival analysis revealed that low TRIM3 expression was associated with poor survival in HCC patients. Finally, our multivariate Cox regression analysis showed that TRIM3 expression was an independent prognostic factor for overall survival of HCC patients. In conclusion, this study suggests that TRIM3 may play a significant role in HCC progression and acts as a valuable prognostic marker and potential therapeutic target for HCC.

Mei-P26 mediates tissue-specific responses to the Brat tumor suppressor and the dMyc proto-oncogene in Drosophila

TRIM-NHL proteins are a family of translational regulators that control cell growth, proliferation, and differentiation during development. Drosophila Brat and Mei-P26 TRIM-NHL proteins serve as tumor suppressors in stem cell lineages and have been proposed to exert this action, in part, via the repression of the protooncogene dMyc. Here we analyze the role of Brat, Mei-P26, and dMyc in regulating growth in Drosophila imaginal discs. As in stem cell lineages, Brat and Mei-P26 repress dMyc in epithelial cells by acting at the post-transcriptional and protein level, respectively. Analysis of cell and organ size unravel that Mei-P26 mediates tissue-specific responses to Brat and dMyc activities. Loss-of-function of brat and overexpression of dMyc induce overgrowth in stem cell lineages and eventually can participate in tumor formation. In contrast, an increase in Mei-P26 levels inhibits growth of epithelial cells in these two conditions. Upon depletion of Brat, Mei-P26 up-regulation prevents an increase in dMyc protein levels and leads to tissue undergrowth. This mechanism appears to be tissue-specific since Mei-P26 is not upregulated in brain tumors resulting from brat loss-of-function. Driving Mei-P26 expression in these tumors -mimicking the situation in epithelial cells- is sufficient to prevent dMyc accumulation, thus rescuing the overgrowth. Finally, we show that Mei-P26 upregulation mediates dMyc-induced apoptosis and limits dMyc growth potential in epithelial cells. These findings shed light on the tumor suppressor roles of TRIM-NHL proteins and underscore a new mechanism that maintains tissue homeostasis upon dMyc deregulation.

Human Brat ortholog TRIM3 is a tumor suppressor that regulates asymmetric cell division in glioblastoma

Cancer stem cells, capable of self-renewal and multipotent differentiation, influence tumor behavior through a complex balance of symmetric and asymmetric cell divisions. Mechanisms regulating the dynamics of stem cells and their progeny in human cancer are poorly understood. In Drosophila, mutation of brain tumor (brat) leads to loss of normal asymmetric cell division by developing neural cells and results in a massively enlarged brain composed of neuroblasts with neoplastic properties. Brat promotes asymmetric cell division and directs neural differentiation at least partially through its suppression on Myc. We identified TRIM3 (11p15.5) as a human ortholog of Drosophila brat and demonstrate its regulation of asymmetric cell division and stem cell properties of glioblastoma (GBM), a highly malignant human brain tumor. TRIM3 gene expression is markedly reduced in human GBM samples, neurosphere cultures, and cell lines and its reconstitution impairs growth properties in vitro and in vivo. TRIM3 expression attenuates stem-like qualities of primary GBM cultures, including neurosphere formation and the expression of stem cell markers CD133, Nestin, and Nanog. In GBM stem cells, TRIM3 expression leads to a greater percentage dividing asymmetrically rather than symmetrically. As with Brat in Drosophila, TRIM3 suppresses c-Myc expression and activity in human glioma cell lines. We also demonstrate a strong regulation of Musashi-Notch signaling by TRIM3 in GBM neurospheres and neural stem cells that may better explain its effect on stem cell dynamics. We conclude that TRIM3 acts as a tumor suppressor in GBM by restoring asymmetric cell division.

The ability of TRIM3 to induce growth arrest depends on RING-dependent E3 ligase activity

Mutation of the TRIM (tripartite motif)-NHL family members brat and mei-P26 perturb the differentiation of transit-amplifying progenitor cells resulting in tumour-like phenotypes. The NHL (named after the NCL1, HT2A and LIN41 repeat) domain is essential for their growth suppressive activity, and they can induce cell-cycle exit in a RING-independent manner. TRIM3 is the only bona fide tumour suppressor in the mammalian TRIM-NHL subfamily and similar to the other members of this family, its ability to inhibit cell proliferation depends on the NHL domain. However, whether the RING domain was required for TRIM3-dependent cell-cycle exit had not been investigated. In the present study, we establish that the RING domain is required for TRIM3-induced growth suppression. Furthermore, we show that this domain is necessary to promote ubiquitination of p21 in a reconstituted in vitro system where UbcH5a is the preferred E2. Thus the ability of TRIM3 to suppress growth is associated with its ability to ubiquitinate proteins.

Asymmetric cell division of stem and progenitor cells during homeostasis and cancer

Stem and progenitor cells are characterized by their ability to self-renew and produce differentiated progeny. A fine balance between these processes is achieved through controlled asymmetric divisions and is necessary to generate cellular diversity during development and to maintain adult tissue homeostasis. Disruption of this balance may result in premature depletion of the stem/progenitor cell pool, or abnormal growth. In many tissues, including the brain, dysregulated asymmetric divisions are associated with cancer. Whether there is a causal relationship between asymmetric cell division defects and cancer initiation is as yet not known. Here, we review the cellular and molecular mechanisms that regulate asymmetric cell divisions in the neural lineage and discuss the potential connections between this regulatory machinery and cancer.